 /*
  * rfc931_user() speaks a common subset of the RFC 931, AUTH, TAP and IDENT
  * protocols. It consults an RFC 931 etc. compatible daemon on the client
  * host to look up the remote user name. The information should not be used
  * for authentication purposes.
  * 
  * Diagnostics are reported through syslog(3).
  * 
  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
  * 
  * Inspired by the authutil package (comp.sources.unix volume 22) by Dan
  * Bernstein (brnstnd@kramden.acf.nyu.edu).
  */

#if 0
static char sccsid[] = "@(#) rfc931.c 1.4 93/03/07 22:47:52";
#endif

#include <stdio.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <setjmp.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

/*#include "log_tcp.h"*/

#define	RFC931_PORT	113     /* Semi-well-known port */

#ifndef RFC931_TIMEOUT
#define	RFC931_TIMEOUT	30      /* wait for at most 30 seconds */
#endif

static jmp_buf timebuf;

/* timeout - handle timeouts */

static void timeout(int sig)
{
    longjmp(timebuf, sig);
}

/* rfc931_name - return remote user name */

char *my_rfc931_name(herefd, there)
int herefd;
struct sockaddr_in *there;      /* remote link information */
{
    struct sockaddr_in here;    /* local link information */
    struct sockaddr_in sin;     /* for talking to RFC931 daemon */
    socklen_t length;
    int s;
    unsigned remote;
    unsigned local;
    static char user[256];      /* XXX */
    char buffer[512];           /* YYY */
    FILE *fp;
    char *cp;
    char *result = "unknown";

    /*
     * Find out local address and port number of stdin. 
     */

    length = sizeof(here);
    if (getsockname(herefd, (struct sockaddr *) &here, &length) == -1) {
        syslog(LOG_ERR, "getsockname: %m");
        return (result);
    }
    /*
     * The socket that will be used for user name lookups should be bound
     * to the same local IP address as stdin. This will automagically
     * happen on hosts that have only one IP network address. When the
     * local host has more than one IP network address, we must do an
     * explicit bind() call.
     */

    if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        return (result);

    sin = here;
    sin.sin_port = 0;
    if (bind(s, (struct sockaddr *) &sin, sizeof sin) < 0) {
        //syslog(LOG_ERR, "bind: %s: %m", inet_ntoa(here.sin_addr));
        syslog(LOG_ERR, "bind: error"); // who cares! atppp 20060415
        return (result);
    }
    /*
     * Set up timer so we won't get stuck. 
     */

    signal(SIGALRM, timeout);
    if (setjmp(timebuf)) {
        close(s);               /* not: fclose(fp) */
        return (result);
    }
    alarm(RFC931_TIMEOUT);

    /*
     * Connect to the RFC931 daemon. 
     */

    sin = *there;
    sin.sin_port = htons(RFC931_PORT);
    if (connect(s, (struct sockaddr *) &sin, sizeof(sin)) == -1 || (fp = fdopen(s, "w+")) == 0) {
        close(s);
        alarm(0);
        return (result);
    }
    /*
     * Use unbuffered I/O or we may read back our own query. setbuf()
     * must be called before doing any I/O on the stream. Thanks for the
     * reminder, Paul Kranenburg <pk@cs.few.eur.nl>!
     */

    setbuf(fp, (char *) 0);

    /*
     * Query the RFC 931 server. Would 13-byte writes ever be broken up? 
     */

    fprintf(fp, "%u,%u\r\n", ntohs(there->sin_port), ntohs(here.sin_port));
    fflush(fp);
    /*
     * Read response from server. Use fgets()/sscanf() instead of
     * fscanf() because there is no buffer for pushback. Thanks, Chris
     * Turbeville <turbo@cse.uta.edu>.
     */

    if (fgets(buffer, sizeof(buffer), fp) != 0
        && ferror(fp) == 0 && feof(fp) == 0 && sscanf(buffer, "%u , %u : USERID :%*[^:]:%255s", &remote, &local, user) == 3 && ntohs(there->sin_port) == remote && ntohs(here.sin_port) == local) {
        /*
         * Strip trailing carriage return. 
         */

        if ((cp = strchr(user, '\r')) != NULL)
            *cp = 0;
        result = user;
    }
    alarm(0);
    fclose(fp);
    return (result);
}

